A conventional size-adjustable skate comprises a set of detachable shoe body and toecap. A size-adjusting structure is disclosed, for instance, in Chinese Patent Application 200420094683.3, wherein long groove holes adjustable in the longitudinal direction and in engagement with each other are disposed at a front end of the shoe body and at the toecap, and an eccentric cam fastening mechanism is disposed on the shoe body. The eccentric cam fastening mechanism comprises an eccentric cam, a rotational handle, a rotatable pin shaft and a cam sheath adjustable stand, of which the eccentric cam and the rotational handle are secured on the rotatable pin shaft, the cam sheath adjustable stand goes through the adjustable long groove holes of the shoe body and the toecap, and the eccentric cam is removably sheathed inside the cam sheath adjustable stand and is rotatable therein. The cam sheath adjustable stand is of a T shape, on which is disposed a cam hole having an aperture two times bigger than the bigger radius of the eccentric cam. Due to the arrangement of an eccentric cam fastening mechanism, this product is capable of being adjusted as to the position of the toecap with regard to the shoe body when the bigger radius of the cam faces upwards, that is to say, the size of the shoe is adjusted thereby, while the shoe body and the toecap are fastened when the bigger radius of the cam faces downwards. Its size-adjusting fastening mechanism is relatively complicated in structure, and it is therefore necessary to make further improvement and perfection thereto.